Background: Previous studies suggest that group therapies, including acceptance and commitment therapy (ACT) and logotherapy, successfully reduce stress in patients.Objectives: The present study aimed to compare the effectiveness of acceptance and commitment group therapy and group logotherapy in reducing perceived stress among multiple sclerosis (MS) patients.Materials and Methods: This research was a pretest-posttest controlled quasi-experimental study. Research population was comprised of all (n=3000) MS patients who were members of Mashhad MS Society, Iran. From among 198 patients, 33 who met the inclusion criteria and scored above 45 on the Perceived Stress Scale (PSS) were selected through convenience sampling, homogenized based on their scores on PSS as well as demographic characteristics, and then assigned to three groups of 11. The first group received 12 ACT sessions and the second group received 8 sessions of group logotherapy, while no intervention was provided for the control group. Afterwards, the PSS was re-administered to all the groups. Data were analyzed using one-way ANCOVA in SPSS software version 20.Results: The results demonstrated that both group therapies reduced perceived stress among patients (p=0.001). However, ACT had a higher effect than logotherapy in reducing perceived stress (p=0.04).Conclusion: Acceptance and commitment group therapy and group logotherapy are effective in reducing perceived stress among MS patients.